I'm a former iPhone user (original, 3gs) and longtime AT&T user (10+ years) that recently switched to Android on Sprint. My best advice is to get very familiar with the phone you're selecting as so you're sure that it meets your needs. Unlike the iPhone, Android devices come in a variety of different hardware types running different software versions and using different launchers. The naysayers call this fragmentation, the fans call it choice. It my opinion, the truth is somewhere in the middle.
A good example of this was that I was interested in the Samsung Epic but really liked the weather/clock widget on the Evo that my wife picked out. Being an iPhone user, I assumed that the widget would also work on the Samung. Well, it won't. Likewise the interfaces and primary apps (contacts, phone, etc.) on the two devices are different enough to warrant some confusion. They actually even use different web browsers.
In the end, we purchased the two Evos and we're reasonably happy. I wouldn't say they're nearly as easy to use as the iPhone and they have many, many quirks, but they also offer some advantages. Again, the best advice I can give is to just do your research firsthand.